By Brendan O'Brien
MILWAUKEE (Reuters) - An unseasonable winter storm system dropped more than 1 foot of snow across the central Plains and the upper Midwest on Thursday, closing roads and causing power outages in Minnesota and Wisconsin, according to the National Weather Service.
The system has resulted in about 18 inches of snow falling in parts of northwest Wisconsin and more than 15 inches in southern Minnesota, the National Weather Service reported.
"This is fairly unusual. The northernmost areas have seen snow in May before, but not of this magnitude," said Jim Keeney, a meteorologist for the National Weather Service.
Temperatures fell close to 30 degrees Fahrenheit (-1 C), making for a heavy, wet snow, causing downed trees, power outages and road closures, Keeney said.
The snowfall will likely break seasonal records in portions of Wisconsin and Minnesota, Keeney predicted.
The National Weather Service has issued winter storm warnings from southeast Minnesota to northwest Wisconsin and weather advisories for eastern Colorado and the upper Midwest that will continue throughout Thursday.
Total snow accumulation is expected to be 10 to 20 inches in the Rockies with up to 6 inches in the Denver area, the National Weather Service said. Between 2 to 6 inches of snow is predicted for portions of the central plains and the upper Midwest.
The system is also bringing a cold rain to western Oklahoma, central Kansas and parts of southwest Iowa, according to the National Weather Service.
The National Weather Service expects the storm to continue overnight Thursday before tapering off Friday afternoon.
(Reporting By Brendan O'Brien; Editing by Scott Malone and Chizu Nomiyama)